Shell Programming and Scripting

there is no such pattern in the filename and no replacement and that is what is meant to be done !!!

for the above req,
it could be done in single step

Code:

echo "filename.Gz.timestamp" | sed 's/\(.*\)\.\(.*\)\.\(.*\)/\1.\3.gz/'

I think I lost you there when you said, there is no pattern. I tried the folllowing code for a compressed file and it works:

filename.z.timestamp
filename.Z.timestamp

echo $filename|sed 's/.[zZ]././'

If above regular expression '[list of values]' works, why the one with '|' does not?

Because in regular expressions the | (pipe) symbol can mean "or", depending on your regex engine.

Instead of chipping away at this, consider reading J Friedl 'Mastering Regular Expressions' that way you'll know why.

again its the problem of pattern that is not matched,

if at all if you want to knock it down the same way you had specified,
just extend the solution,

Code:

echo $filename  | sed 's/.[gG][zZ]././'

Thanks for your reply and i guess I am still confused. By using a '|', i meant to imply an 'or' to sed. I was telling it to convert either .gz. or .gZ. or .GZ. or .Gz. to a dot

It should not consider the '|' operator as pipe to another command as i am using it within the arguments of sed.

I am still hoping there should be some rationale behind it.

Matrixmadhan

I dont think that would be a very clean way to do it.. I mean if there is something like '|' that is allowed in regular expression and if it is supposed to work with sed, it should, right? Leaving aside all the possible solution, i guess i am more interested to know what is wrong with a use of '|'.

If it works with sed the way you said it does, what is the correct usage?

the symbol '|' you use in sed is just a '|'

when you use '|' in the sed to replace from the text, from the input string a pattern that matches inclusive of '|' is searched for.. if it finds it would replace

simplest example could be

echo "a|b" | sed 's/|/u/'
aub

it is just '|' not a pipe operator or an OR condition,
just a part of or a complete pattern by itself,

hope i am answering to what you have aksed for,
if not plz let me know